Safety system for a gas apparatus for heating water

ABSTRACT

A safety system for a gas apparatus (100) for heating water, the gas apparatus comprising a tank (1) for containing water and a first gas burner (2) for heating the water contained inside the tank (1). The safety system (200, 200′) comprises a first sensor (9) suitable for generating a first signal which represents a temperature of the water contained in the tank (1), a second sensor (10) suitable for generating a second signal which represents a temperature of the water contained in the tank (1), a supply circuit (11) for energizing a first actuator (4) of a first valve (3) which is arranged to allow to pass/intercept a flow of gas towards the first gas burner (2), the first actuator (4) being arranged to actuate so as to open and close the first valve (3) when it is energized and non-energized, respectively, a switch device (13) which is arranged in the supply circuit (11) in order to close/open the supply circuit (11) so as to energize/not to energize the first actuator (4), a digital processing unit (14) which is operatively connected to the first and/or second sensor (9, 10) and which is configured to compare a set-point value which represents a preselected temperature with the first or second signal and a control device (16) which is operatively connected to the switch device (13) and to the first and second sensors (9, 10). The control device (16) comprises an analogue comparator (17) which is operatively connected to the first and second sensors (9, 10) in order to compare the first signal with the second signal and the control device (16) is configured to generate a control signal (18) for controlling so as to open/close the switch device (13) on the basis of the comparison between the first and second signals carried out by the analogue comparator (17).

TECHNICAL FIELD

The present invention relates to a safety system for a gas apparatus forheating water, a gas apparatus comprising such a safety system and amethod for controlling the above-mentioned gas apparatus.

TECHNOLOGICAL BACKGROUND

The invention is used particularly though not exclusively in the fieldof producing and using devices for heating gas, that is to say, devicesfor heating by means of a gas burner. In a preferable manner, theinvention is used in installations for heating water, such as, forexample, boilers. In this field of use, there are known devices forheating water which are provided with a gas burner for heating the watercontained in a tank and at least two temperature sensors which areprovided to generate a respective signal which represents thetemperature measured by it in respect of the water contained in thistank.

Typically, these devices are provided with a control system whichcomprises a digital logic unit for controlling the lighting/shutdown ofthe gas burner on the basis of the temperature detected by one of theabove-mentioned sensors. The temperature detected by the second sensoris instead used by the digital logic unit to carry out a check of thecorrectness of the temperature measured by the first sensor, that is tosay, in order to control the correct operation of the heating device.

A limitation of this solution may be defined as an energy consumptionwhich is excessive, or not negligible, of the control system forestablishing the correct operation of the heating device.

SUMMARY OF INVENTION

An object of the present invention is to provide a safety system for agas apparatus for heating water, a gas apparatus comprising such asafety system and a method for controlling the above-mentioned gasapparatus which is structurally and operatively configured to overcomeat least one above-indicated limitation with reference to the knownsolutions.

This object is achieved by means of a safety system for a gas apparatusfor heating water, a gas apparatus comprising such a safety system and amethod for controlling the above-mentioned gas apparatus which areachieved in accordance with the respective independent claims which areappended to the present description.

Preferred features of the invention are defined in the dependent claims.According to a first aspect of the invention, a safety system for a gasapparatus for heating water comprises a first sensor and a second sensorsuitable for generating a first signal and a second signal,respectively, which represent a temperature of the water contained in atank of the gas apparatus.

The first sensor and the second sensor are preferably temperaturesensors. According to a first aspect of the invention, the first andsecond signals are analogue electrical signals, preferably in terms ofvoltage.

According to an aspect of the invention, the first sensor and the secondsensor are arranged inside the tank, preferably in an intermediate zonethereof. Preferably, the first sensor and the second sensor arepositioned so as to measure the temperature of the same portion of thewater contained in the tank. The first sensor may be adjacent to thesecond sensor.

The gas apparatus comprises, in addition to the tank for containingwater, a first gas burner for heating the water which is containedinside that tank. According to an aspect of the invention, the gasapparatus may be identified as a boiler.

The gas apparatus may comprise a first valve which is arranged to allowto pass/intercept a flow of gas towards the first gas burner. The gasapparatus may comprise a first actuator which is arranged to actuate soas to open and close the first valve when it is energized andnon-energized, respectively.

According to an aspect of the invention, the safety system comprisesa(n) (electrical) supply circuit for energizing the first actuator ofthe first valve. The first actuator is connected to the supply circuit.

According to an aspect of the invention, the supply circuit is connectedto an electrical energy generator which is capable of energizing thissupply circuit. The electrical energy generator is preferably athermoelectric generator, for example, it is a thermopile orthermocouple.

According to an aspect of the invention, the thermoelectric generator isassociated with a gas burner, the generated flame of which energizes thethermoelectric generator.

According to a first embodiment of the invention, the thermoelectricgenerator may be associated with the generated flame of the first gasburner.

According to an aspect of the invention, the first actuator is energizedby a voltage which is correlated with the voltage generated by theelectrical energy generator via the supply circuit.

According to a second embodiment of the invention, the gas apparatuscomprises a second gas burner and a second actuator which is provided toactuate so as to open and close a second valve of the gas apparatus whenit is energized and non-energized, respectively.

The second valve is arranged to allow to pass/intercept a flow of gastowards the second gas burner and, preferably, towards the first gasburner. In particular, the second valve is arranged to allow topass/intercept a flow of gas towards the second gas burner and, in acascading manner, towards the first gas burner.

Preferably, the second valve is positioned upstream of the first valvewith respect to the direction of flow of the gas flow.

According to an aspect of the invention, the second actuator isconnected to the above-mentioned supply circuit and is preferablyenergized by means of the electrical energy generator, in particular thethermoelectric generator, which energizes the first actuator. In thiscase, this thermoelectric generator is preferably associated with thesecond gas burner in place of the first gas burner so as to be energizedby the flame generated by the second gas burner.

Preferably, the first valve and the first gas burner represent a mainvalve and a main burner, respectively, of the gas apparatus while thesecond valve and the second gas burner represent a pilot valve and apilot burner of the gas apparatus, respectively. The pilot burner isintended to light the main burner by means of the relevant pilot flame.

According to an aspect of the invention, the safety system comprises aswitch device which is arranged in the supply circuit in order toclose/open this supply circuit so as to energize/not to energize thefirst actuator.

It is evident that, in the embodiment of the invention in which the gasapparatus is provided with the first burner and second burner, theclosure/opening of the supply circuit via the switch device brings aboutthe energization/non-energization both of the first actuator and of thesecond actuator.

According to an aspect of the invention, the safety system comprises adigital processing unit which is operatively connected to the firstand/or second sensor.

The digital processing unit is configured to compare a set-point valuewhich represents a preselected temperature with the first or secondsignal.

The digital processing unit may be a microcontroller.

Additionally or alternatively, the digital processing unit may comprisean integrated circuit ASIC (Application-Specific Integrated Circuit) andoptionally an additional digital logic unit in order to operateaccording to the invention.

According to an aspect of the invention, the digital processing unit issupplied by an electrical energy generator via a relevant electricalcircuit which connects the digital processing unit to the electricalenergy generator. This electrical energy generator may be athermoelectric generator or a battery.

This thermoelectric generator is associated with a gas burner, thegenerated flame of which energizes the thermoelectric generator.Preferably, this thermoelectric generator is the same one whichenergizes the supply circuit of the safety system.

According to an aspect of the invention, the digital processing unit isoperatively connected to the first and/or second actuator, in particularit is connected to the supply circuit of the above-mentioned actuators(for example, via the above-mentioned switch device or by means of asecond switch device) and is configured to actuate the first and/orsecond actuator on the basis of a comparison between the set-point valueand the first (or second) signal, preferably on the basis of adifference between the above-mentioned signals.

In particular, the digital processing unit is configured to actuate thefirst actuator in order to allow to pass or intercept a flow of gastowards the gas burner and/or the second actuator in order to allow topass or intercept a flow of gas towards the second gas burner andpreferably towards the first gas burner on the basis of a comparisonbetween the set-point value and the first (or second) signal.

By way of example, the first actuator is actuated so as to open by thedigital processing unit if the difference between the set-point valueand the first (or second) signal is less than or equal to a predefinedthreshold while the digital processing unit actuates so as to close thefirst actuator if this difference is greater than the above-mentionedthreshold.

According to an aspect of the invention, the safety system comprises acontrol device which is operatively connected to the switch device, tothe first sensor and to the second sensor.

According to an aspect of the invention, the control device may besupplied by an electrical energy generator via a relevant electricalcircuit which connects the control device to this electrical energygenerator. This electrical energy generator may be a thermoelectricgenerator or a battery. This thermoelectric generator is associated witha gas burner, the generated flame of which energizes the thermoelectricgenerator. Preferably, this thermoelectric generator is the same onewhich energizes the supply circuit of the safety system and/or thedigital processing unit.

The control device may comprise the digital processing unit.

The control device comprises an analogue comparator which is operativelyconnected to the first sensor and second sensor in order to compare thefirst signal with the second signal.

According to an aspect of the invention, the control device isconfigured to generate a control signal for controlling so as toopen/close the switch device on the basis of the comparison between thefirst signal and the second signal which is carried out by the analoguecomparator.

In other words, the control device is configured for controlling so asto open/close the switch device by means of a control signal which isgenerated on the basis of a comparison between the first signal and thesecond signal.

The control signal may be a digital signal, preferably with two levelsof voltage.

The comparison between the signals which are generated by the twosensors is therefore carried out by an analogue comparator without theinvolvement of the digital processing unit, with a resultant saving interms of electrical energy consumption. In fact, in the event that thedigital processing unit has to compare the first signal with the secondsignal so that the control device generates the control signal, theseanalogue signals have to be subjected to an analogue/digital conversionupstream of the comparison which inevitably requires greater use ofelectrical energy with respect to the analogue comparison according tothe invention.

The use of an analogue comparator does not therefore require additionalprocessing steps for the signals which are generated by the first sensorand the second sensor, thereby reducing the absorption of energyrequired by the control device for generating the control signal.

This feature is found to be particularly advantageous if the electricalenergy generator which energizes the supply circuit and the digitalprocessing unit is a thermoelectric generator.

According to an aspect of the invention, the analogue comparator isoperatively connected to the switch device and is capable of generatingthe control signal for controlling so as to open/close the switch deviceon the basis of the comparison between the first signal and the secondsignal.

In this manner, the analogue comparator directly controls the closure ofthe first valve and therefore the shutdown of the first burner withoutusing additional electronic components.

According to an aspect of the invention, the analogue comparator iscapable of generating the control signal for controlling so as to openthe switch device if the difference between the first signal and thesecond signal is greater than a predefined value and for controlling soas to close the switch device if the difference between the first signaland the second signal is less than or equal to the above-mentionedpredefined value.

According to an aspect of the invention, the above-mentioned predefinedvalue is less than or equal to 0.5 mV. Preferably, this predefined valueis between 0.2 mV and 0.5 mV.

According to an aspect of the invention, the control device comprisesthe above-mentioned digital processing unit.

According to an aspect of the invention, the analogue comparator isoperatively connected to the digital processing unit and is capable ofgenerating an output signal on the basis of the comparison between thefirst signal and second signal.

Preferably, the output signal is a digital signal which can take on afirst value and a second value, in particular a first voltage value anda second voltage value.

The first value may be equal to 0 V (first voltage level) and the secondvalue may be equal to 5 V (second voltage level).

According to an aspect of the invention, the digital processing unit isoperatively connected to the switch device and is capable of generatingthe control signal for controlling so as to close the switch device whenthe output signal takes on the first value and for controlling so as toopen the switch device when the output signal takes on the second value.

This feature allows control of the switch device by means of the digitalprocessing unit, but maintaining the burden of the comparison betweenthe first signal and second signal with respect to the analoguecomparator. According to an aspect of the invention, the analoguecomparator is capable of generating the second value of the outputsignal if the difference between the first signal and the second signalis greater than a predefined value. The analogue comparator is insteadcapable of generating the first value of the output signal if thedifference between the first signal and the second signal is less thanor equal to the above-mentioned predefined value. According to an aspectof the invention, the above-mentioned predefined value is less than orequal to 0.5 mV. Preferably, this predefined value is between 0.2 mV and0.5 mV.

According to an aspect of the invention, the safety system comprises asignalling device which is operatively connected to the control deviceand/or to the digital processing unit and is provided to generate awarning signal on the basis of the value which is taken on by the outputsignal which is generated by the analogue comparator.

The warning signal may be an audible signal and/or illuminated signal soas to communicate to a user of the safety system the result of thecomparison between the first signal and the second signal which aregenerated by the respective sensors. By way of example, the signallingdevice comprises a buzzer and/or one or more LED devices.

The signalling device may therefore not emit any audible/illuminatedsignal, or may emit a first illuminated signal, if the output signaltakes on the first value and may emit an audible signal and/or a secondilluminated signal which is different from the first signal (forexample, in terms of number of LED devices illuminated and/or colouremitted) if the output signal takes on the second value.

According to an aspect of the invention, the gas apparatus may comprisethe safety system which is provided with at least one of theabove-described features or a combination of two or more of theabove-described features. Furthermore, the gas apparatus may comprisethe thermoelectric generator, preferably a thermopile, in order toenergize the supply circuit and/or the digital processing unit.

According to an aspect of the invention, a method for controlling thegas apparatus for heating water comprises:

-   -   generating a first signal which represents a temperature of the        water contained in the tank of the gas apparatus by means of the        first sensor of the gas apparatus,    -   generating a second signal which represents a temperature of the        water contained in the tank of the gas apparatus by means of the        second sensor of the gas apparatus,    -   comparing the first signal with the second signal by means of        the analogue comparator of the gas apparatus,    -   generating a control signal by means of the control device of        the gas apparatus on the basis of the comparison between the        first and second signals,    -   controlling so as to close/open the switch device of the gas        apparatus by means of the control signal so as to energize/not        to energize the first actuator of the gas apparatus.

According to an aspect of the invention, the first temperature sensorand the second temperature sensor measure in a continuous orintermittent manner (for example, each minute or more generally inaccordance with a pre-established interval) the temperature of the watercontained in the tank. According to an aspect of the invention, thecomparison between the first signal and the second signal is carried outin a continuous or intermittent manner (for example, each minute or moregenerally in accordance with a pre-established interval).

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of the invention will be better appreciated fromthe following detailed description of preferred embodiments thereofwhich are illustrated by way of non-limiting example with reference tothe appended Figures, in which:

FIG. 1 is a schematic view of a gas apparatus according to theinvention,

FIG. 2 is a schematic view of a first embodiment of a safety systemaccording to the invention,

FIG. 3 is a schematic view of a second embodiment of a safety systemaccording to the invention.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

With reference initially to FIG. 1, there is generally designated 100 agas apparatus for heating water which is constructed according to thepresent invention.

The gas apparatus 100 comprising a tank 1 for containing water, a firstgas burner 2 for heating the water which is contained inside the tank 1,a first valve 3 which is provided to allow to pass/intercept a flow ofgas towards the first gas burner 2, a first actuator 4 arranged toactuate so as to open and close the first valve 3 when it is energizedand non-energized, respectively, and a safety system according to theinvention.

The gas apparatus 100 further comprises a second gas burner 6, a secondvalve 7 which is provided to allow to pass/intercept a flow of gastowards the first and second gas burners 2, 6 and a second actuator 8arranged to actuate so as to open and close the second valve 7 when itis energized and non-energized, respectively.

The first valve 3 and the first gas burner 2 represent a main valve anda main burner of the gas apparatus 100, respectively, while the secondvalve 7 and the second gas burner 6 represent a pilot valve and a pilotburner of the gas apparatus 100, respectively.

FIG. 2 shows a first embodiment of the safety system according to theinvention which is generally designated 200.

The safety system 200 comprises a first and a second sensor 9, 10 whichare capable of generating a first and a second signal which represent atemperature of the water contained in the tank 1, respectively. Inparticular, the first and second sensors 9, 10 are temperature sensorswhich are configured to generate a respective analogue signal in termsof voltage.

The safety system 200 further comprises a supply circuit 11 forenergizing the first actuator and the second actuator 4, 8. The firstactuator and the second actuator 4, 8 are therefore connected to thesupply circuit 11 via which they are energized by a thermoelectricgenerator 12, in particular a thermopile. The thermoelectric generator12 is associated with the second gas burner 6 so as to be energized bythe flame which is generated by this gas burner.

The safety system 200 comprises a switch device 13 which is arranged inthe supply circuit 11 to close/open the supply circuit 11 so as toenergize/not energize the first and the second actuators 4, 8.

The safety system 200 further comprises a digital processing unit 14which is operatively connected to the first sensor 9 and which isconfigured to compare a set-point value which represents a preselectedtemperature with the first signal.

In particular, the digital processing unit 14 is a microcontroller whichis supplied by the thermoelectric generator 12 via a relevant electricalcircuit 21 which may comprise a DC/DC converter.

The digital processing unit 14 is operatively connected to the supplycircuit 11 by means of a second switch device 5 in order to actuate thefirst and the second actuators 4, 8 on the basis of a comparison betweenthe set-point value and the first signal, preferably on the basis of adifference between the signals mentioned above.

The set-point value may be selected manually by a user by means of aknob 15 or other known input device.

In addition, the safety system 200 comprises a control device 16 whichis operatively connected to the switch device 13 and the first andsecond is sensors 9, 10.

The control device 16 may comprise the digital processing unit 14. Thecontrol device 16 comprises an analogue comparator 17 which isoperatively connected to the first and second sensors 9, 10 in order tocompare the first signal with the second signal.

The control device is further configured to generate a control signal 18for controlling so as to open/close the switch device 13 on the basis ofthe comparison between the first signal and the second signal carriedout by the analogue comparator 17.

In particular, the analogue comparator 17 is operatively connected tothe switch device 13 and is capable of generating the control signal 18for controlling so as to open/close the switch device 13 on the basis ofthe comparison between the first signal and the second signal.

Specifically, the analogue comparator 17 is capable of generating thecontrol signal 18 for controlling so as to open the switch device 13 ifthe difference between the first signal and the second signal is greaterthan a predefined value and for controlling so as to close the switchdevice 13 if the difference between the first signal and the secondsignal is less than or equal to this predefined value.

Preferably, the predefined value is equal to 0.2 mV or 0.5 mV. FIG. 3shows a second embodiment of the safety system according to theinvention which is generally designated 200′.

The features of the safety system 200′ in common with those of thesafety system 200 shown in FIG. 2 are indicated with the same referencenumeral.

With reference to FIG. 3, the analogue comparator 17 is operativelyconnected to the digital processing unit 14 and is capable of generatingan output signal 19 on the basis of the comparison between the firstsignal and the second signal.

The control device 16 comprises the digital processing unit 14, which isoperatively connected to the switch device 13. In addition, the digitalprocessing unit 14 is capable of generating the control signal 18 forcontrolling so as to close the switch device 13 when the output signal19 takes on a first value and for controlling so as to open the switchdevice 13 when the output signal 19 takes on a second value.

In particular, the analogue comparator 17 is capable of generating thesecond value of the output signal 19 if the difference between the firstsignal and the second signal is greater than a predefined value whilethe first value of the output signal 19 is generated by the analoguecomparator 17 if the difference between the first signal and the secondsignal is less than or equal to this predefined value.

Preferably, the predefined value is equal to 0.2 mV or 0.5 mV.

The safety system 200′ further comprises a signalling device 20 which isoperatively connected to the digital processing unit 14 and which isprovided to generate an audible and/or illuminated warning signal on thebasis of the value taken on by the output signal 19 which is generatedby the analogue comparator 17. Specifically, the signalling device 20comprises a buzzer and a plurality of LED devices and does not emit anyaudible/illuminated signal if the output signal 19 takes on the firstvalue, and emits an audible signal and/or illuminated signal if theoutput signal 19 takes on the second value.

The invention thereby achieves the objects set out, affording theadvantages mentioned above with respect to the known solutions.

1. A safety system for a gas apparatus (100) for heating water, the gasapparatus comprising a tank (1) for containing water and a first gasburner (2) for heating the water contained inside the tank (1), thesafety system (200, 200′) comprising: a first sensor (9) suitable forgenerating a first signal which represents a temperature of the watercontained in the tank (1), a second sensor (10) suitable for generatinga second signal which represents a temperature of the water contained inthe tank (1), a supply circuit (11) for energizing a first actuator (4)of a first valve (3) which is arranged to allow to pass/intercept a flowof gas towards the first gas burner (2), the first actuator (4) beingarranged to actuate so as to open and close the first valve (3) when thefirst actuator is energized and non-energized, respectively, a switchdevice (13) which is arranged in the supply circuit (11) in order toclose/open the supply circuit (11) so as to energize/not to energize thefirst actuator (4), a digital processing unit (14) which is operativelyconnected to the first and/or second sensor (9, 10) and which isconfigured to compare a set-point value which represents a preselectedtemperature with the first or second signal and a control device (16)which is operatively connected to the switch device (13) and to thefirst and second sensors (9, 10), the control device (16) comprises ananalogue comparator (17) which is operatively connected to the first andsecond sensors (9, 10) in order to compare the first signal with thesecond signal and the control device (16) is configured to generate acontrol signal (18) for controlling so as to open/close the switchdevice (13) on the basis of the comparison between the first and secondsignals carried out by the analogue comparator (17).
 2. The safetysystem according to claim 1, wherein the analogue comparator (17) isoperatively connected to the switch device (13) and is capable ofgenerating the control signal (18) for controlling so as to open/closethe switch device (13) on the basis of the comparison between the firstand second signals.
 3. The safety system according to claim 2, whereinthe analogue comparator (17) is capable of generating the control signal(18) for controlling so as to open the switch device (13) if adifference between the first signal and the second signal is greaterthan a predefined value and for controlling so as to close the switchdevice (13) if the difference between the first signal and the secondsignal is less than or equal to the predefined value.
 4. The safetysystem according to claim 1, wherein the control device (16) comprisesthe digital processing unit (14), the analogue comparator (17) beingoperatively connected to the digital processing unit (14) and beingcapable of generating an output signal (19) on the basis of a comparisonbetween the first and second signals, the digital processing unit (14)being operatively connected to the switch device (13) and being capableof generating the control signal (18) for controlling so as to close theswitch device (13) when the output signal (19) takes on a first valueand for controlling so as to open the switch device (13) when the outputsignal (19) takes on a second value.
 5. The safety system according toclaim 4, wherein the analogue comparator (17) is capable of generatingthe second value of the output signal (19) if a difference between thefirst signal and the second signal is greater than a predefined value.6. The safety system according to claim 1, wherein the first and secondsignals are analogue electrical signals.
 7. A gas apparatus for heatingwater, the gas apparatus (100) comprising a tank (1) for containingwater, a first gas burner (2) for heating the water contained inside thetank (1), a first valve (3) which is provided to allow to pass/intercepta flow of gas towards the first gas burner (2), a first actuator (4)which is provided to actuate so as to open and close the first valve (3)when it is energized and non-energized, respectively, and a safetysystem (200, 200′) according to claim
 1. 8. The gas apparatus accordingto claim 7, wherein the gas apparatus (100) further comprises athermoelectric generator (12) for energizing the supply circuit (11)and/or the digital processing unit (14).
 9. The gas apparatus accordingto claim 8, wherein the gas apparatus (100) comprises a second gasburner (6), a second valve (7) which is provided to allow topass/intercept a flow of gas towards the second gas burner (6), andtowards the first gas burner (2), and a second actuator (8) which isconnected to the supply circuit (11) and which is provided to actuate soas to open and close the second valve (7) when the second actuator isenergized and non-energized, respectively, the first gas burner (2)being a main burner and the second gas burner (6) being a pilot burnerwhich is configured to light the main burner by means of a relevantpilot flame.
 10. The gas apparatus according to claim 9, wherein thethermoelectric generator (12) is associated with the second burner (6)so as to be energized by the flame generated by the second burner (6).11. A method for controlling a gas apparatus (100) according to claim 7,the method comprising: generating a first signal which represents atemperature of the water contained in the tank (1) of the gas apparatus(100) by means of the first sensor (9) of the gas apparatus (100),generating a second signal which represents a temperature of the watercontained in the tank (1) of the gas apparatus (100) by means of thesecond sensor (10) of the gas apparatus (100), comparing the firstsignal with the second signal by means of the analogue comparator (17)of the gas apparatus (100), generating a control signal (18) by means ofthe control device (16) of the gas apparatus (100) on the basis of thecomparison between the first and second signals and controlling so as toclose/open the switch device (13) of the gas apparatus (100) by means ofthe control signal (18) so as to energize/not to energize the firstactuator (4) of the gas apparatus (100).